1. Field of the Present Invention
The present invention relates generally to wheel covers for motor vehicles, and more particularly to such covers adapted to be retained in position with respect to the wheel by a resilient retaining ring.
2. Description of the Prior Art
It has been known to make wheel covers of a plastic material in order to minimize the weight of the cover or to minimize the expense of making the wheel cover. However, such wheel covers are more susceptible to breakage and distortion than metal wheel covers. In particular, when the means for attaching the wheel cover to the wheel is integrally formed of plastic material with the wheel cover, the forces imposed upon the plastic retaining means can distort the cover as well as the retaining means and reduce the effectiveness of the retaining means. Moreover, when the wheel is subjected to unexpected shocks, the plastic retaining means can be extremely stressed and broken whereby the wheel cover becomes separated from the wheel.
One previously known wheel cover construction intended to alleviate these problems is disclosed in U.S. Pat. No. 4,027,919 to Foster. Foster discloses a wheel cover assembly in which a resilient flexible ring is supported by the wheel cover and resiliently engaged against a portion of the wheel. The projections are formed by return bent portions of spring wire extending through radially aligned apertures formed in axially extending wall portions of the wheel cover. The openings are defined by guide walls dimensioned to peripherally engage the projections to prevent relative axial and circumferential displacement between the retaining ring and the wheel cover.
Nevertheless, while that patent purports to teach that substantially all of the forces for retaining the wheel cover in position on the wheel are absorbed by the ring rather than being transmitted to the cover, the engagement between the projection and the guide walls of the openings transmits loads to the wheel covers and reduces the effective retaining force. Such limitation of the force being exerted on the wheel by the retainer can adversely affect the ability of the wheel cover to retain its position with respect to the wheel. Moreover, in view of the fact that the rounded ends of the projections provide a very small area of engagement with the wheel, the reduction of the retention force substantially affects the ability of the wheel cover to retain its position on the wheel.
Moreover, a substantial amount of torque is applied to the vehicle's wheels during operation of the vehicle. Thus, perhaps the greatest force exerted upon the wheel cover is that which tends to cause relative rotational displacement between the wheel cover and the wheel. The rounded projection of the previously known rings and the limited retention force available in the previously known mounting substantially reduce resistance to circumferential displacement of the ring, and thus the cover, with respect to the wheel. Since the tire valve used for inflating the tire often extends through an opening in the wheel cover, such circumferential displacement can cause deformation and destruction of the tire valve.